1. Field of the Invention
Aspects of the present invention relate to a fuel cell, and more particularly, to a fuel cell that includes a coated layer containing a moisture retentive material between an electrolyte membrane and an anode catalyst layer and/or between the anode catalyst layer and an anode diffusion layer, and thus can stably operate even when a fuel supply is temporarily interrupted.
2. Description of the Related Art
Fuel cells can be categorized into alkali fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid polymer electrolyte fuel cells, solid polymer fuel cells, and the like, according to the electrolytic solution that is used. Among these fuel cells, solid polymer electrolyte fuel cells that can operate at a low temperature, are easy to handle, and have a high output density have been drawing attention as energy sources for electric vehicles, home appliances, and the like.
A solid polymer electrolyte fuel cell includes a proton conductive layer as an electrolyte. The proton conductive layer must have a high ionic conductivity with respect to protons that are involved in an electrode reaction in the fuel cell. Such a proton conductive layer is typically formed of a super-strong acid-containing fluoride polymer. Such polymers are commonly known. For example, NAFION, a trademarked product of DuPont, is a fluoride polymer commonly used as a proton conductive layer. However, fluoride polymers tend to be very expensive and typically must always be humidified, since protons conduct through the medium of water.
U.S. Patent Publication No. 2004/0166397 discloses a direct methanol fuel cell with a membrane electrode assembly (MEA) manufactured by coupling a hydrophobic catalyst layer coated on a backing layer and a non-hydrophobic catalyst layer coated on a roughly treated electrolyte membrane, wherein a hydrophobic treatment is performed on a cathode.
Meanwhile, the performance of conventional fuel cells markedly degrades when a fuel supply is temporarily interrupted, as may happen, for example, when a pump malfunctions or a fuel channel becomes clogged.